#include <bits/stdc++.h>

using namespace std;

bool dp[6][20001];
vector <int> adj[20001];
int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n, m, a, b;

	cin >> n >> m;

	for (int i = 0; i < m; i++)
	{
		cin >> a >> b;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}

	for (int i = 1; i <= 1; i++)
	{
		memset(dp, false, sizeof(dp));
		dp[0][i] = true;
		for (int j = 0; j < 5; j++)
		{
			for (int k = 1; k <= n; k++)
			{
				if (dp[j][k] == false) continue;
				for (auto u : adj[k])
				{
					dp[j + 1][u] = true;
				}
			}
		}
		if (dp[5][i])
		{
			cout << "YES" << '\n';
			return 0;
		}
	}

	cout << "NO" << '\n';

	return 0;
}